Ethylene copolymers having good processability and good physical properties are often made by way of blending two polyethylene compositions together where one resin imparts a desirable level of processability and one resin imparts good physical properties, such as good dart impact or tear resistance properties when the blend is blown into film. In an effort to avoid the need for polymer blending, dual or mixed catalysts strategies have also been developed for use in polymerization reactors. In other cases ethylene copolymers having balanced processability and physical properties have been made using a single catalyst in a single reactor. See, for example, U.S. Pat. Appl. Pub. No. 2014/0100343 which describes the formation of a polyethylene resin made using a phosphinimine catalyst supported on silica.
In addition to standard inert supports such as, for example, silica, single site catalysts have also been supported on so called “passivated support” materials as is described in U.S. Pat. Appl. Pub. No. 2013/0172500.